Blind and confused

A 62-year-old man developed confusion and was diagnosed as having encephalitis. The etiology was not identified. He continued to have cognitive impairment but remained clinically stable. Five months later, he woke with bilateral vision loss. On neurological examination, he had no light perception bilaterally. The remainder of the neurological examination results were normal. Magnetic resonance imaging of the brain revealed multiple brain lesions. He was treated with steroids and plasmapheresis, with mild improvement in vision. He was then transferred to a long-term care facility, where he developed increasing confusion and ultimately died. An autopsy was performed; the differential diagnosis, neuropathology, and final diagnosis are discussed here.